Geos库学习之（四）——几何对象空间关系判断实例

上篇我们主要对几何对象之间的关系做了简单的说明，在GEOS中的方法使做了大概的了解，本篇我们以程序实例对这几种关系进行简单的验证说明，直接上代码：

// GeoTest.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include 
#include 

#include "geos.h"

using namespace std;
using namespace geos;
using namespace geos::geom;

static const GeometryFactory* g_factory = geos::geom::GeometryFactory::getDefaultInstance(); //全局对象,所有的图形都由此对象创建

//单点的创建
Point* createGeosPoint(double x, double y)
{
	Coordinate pt(x, y);    //坐标
	Point* p = g_factory->createPoint(pt);
	return p;
}

//多点的创建
MultiPoint* createGeosMultiPoint(double x, double y, double offset)
{
	CoordinateArraySequence *cas = new CoordinateArraySequence(); //构建点序列
	std::vector points;
	points.push_back(Coordinate(x, y));
	points.push_back(Coordinate(x + offset, y));
	points.push_back(Coordinate(x + 2 * offset, y + offset));
	points.push_back(Coordinate(x + 3 * offset, y + 2 * offset));
	MultiPoint* Mp = g_factory->createMultiPoint(points);
	return Mp;
}

//非闭合线
LineString* createGeosLine(double x, double y, double offset)
{
	CoordinateArraySequence *cas = new CoordinateArraySequence(); //构建点序列
	cas->add(Coordinate(x, y));
	cas->add(Coordinate(x, y + offset));
	cas->add(Coordinate(x + offset, y + offset));
	cas->add(Coordinate(x + offset, y + 2 * offset));
	cas->add(Coordinate(x + 2 * offset, y + 2 * offset));
	LineString *ls = g_factory->createLineString(cas);
	return ls;
}

//创建一条环线，与线的区别就是环线是闭合的。即第一个点和最后一点重合
LinearRing* createGeosRing(double x, double y, double offset)
{
	CoordinateArraySequence *cas = new CoordinateArraySequence(); //构建点序列
	cas->add(Coordinate(x, y));
	cas->add(Coordinate(x, y + offset));
	cas->add(Coordinate(x + offset, y + offset));
	cas->add(Coordinate(x + offset, y + 2 * offset));
	cas->add(Coordinate(x + 2 * offset, y + 2 * offset));
	cas->add(Coordinate(x + 2 * offset, y));
	cas->add(Coordinate(x, y)); //与第一个点相等
	LinearRing *lr = g_factory->createLinearRing(cas);
	return lr;
}

//创建一个多边形，如果多边形内部没有孔洞实际上与环线是一样的
Polygon* createGeosPolygon(double x, double y, double offset)
{
	LinearRing *lr = createGeosRing(x, y, offset);
	Polygon *poly = g_factory->createPolygon(lr, NULL); //如果多边形中间没有孔洞，第二个参数设为NULL
	return poly;
}

int main()
{
	Point* point = createGeosPoint(10, 20);
	std::string typeStr = point->getGeometryType();
	cout << "创建的点类型:" << typeStr << endl;

	MultiPoint* multiPoint = createGeosMultiPoint(10, 20,5);
	int count = multiPoint->getNumPoints();
	

	std::unique_ptr pointIm = multiPoint->relate(point);
	cout << "多点和点之前的关系:  " << *pointIm  << "     ";
	if (multiPoint->disjoint(point))
		cout << "不相交" << endl;
	else
	{
		if (multiPoint->touches(point))
			cout << "接触" << endl;
		else if (multiPoint->overlaps(point))
			cout << "部分重叠" << endl;
		else if (multiPoint->covers(point))
			cout << "覆盖" << endl;
		else
			cout << *pointIm << endl;
	}

	cout << "**************************************************" << endl << endl;

	LineString *ls = createGeosRing(10, 10, 5);
	cout << "线条点数：" << ls->getNumPoints() << " 线条长度：" << ls->getLength() << endl;

	std::unique_ptr lineIm = ls->relate(point);
	cout << "线和点之前的关系:  " << *lineIm << "     ";
	if (ls->disjoint(point))
		cout << "不相交" << endl;
	else
	{
		if (ls->touches(point))
			cout << "接触" << endl;
		else if (ls->overlaps(point))
			cout << "部分重叠" << endl;
		else if (ls->covers(point))
			cout << "覆盖" << endl;
		else
			cout << *lineIm << endl;
	}

	cout << "**************************************************" << endl << endl;

	Polygon *poly = createGeosPolygon(10, 10, 5);
	cout << "多边形面积:" << poly->getArea() << endl;

	std::unique_ptr polygonIm = poly->relate(ls);
	cout << "面和线之前的关系:  " << *polygonIm << "     ";
	if (poly->disjoint(ls))
		cout << "不相交" << endl;
	else
	{
		if (poly->touches(ls))
			cout << "接触" << endl;
		else if (poly->overlaps(ls))
			cout << "部分重叠" << endl;
		else if (poly->covers(ls))
			cout << "覆盖" << endl;
		else
			cout << *polygonIm << endl;
	}

	cout << "**************************************************" << endl << endl;

	Polygon *p1 = createGeosPolygon(12, 12, 5); //创建一个多边形

	for (int i = 0;i <= 20;i++)
	{
		cout << "第" << i << "个面和面之间的关系 " << ":   ";
		Polygon *pPolygon = createGeosPolygon(0, 0, i); //创建第二个多边形
		std::unique_ptr im = pPolygon->relate(p1);
		cout << *im << "    ";    //返回DE-9IM交叉矩阵
		if (pPolygon->disjoint(p1))
			cout << "不相交" << endl;
		else
		{
			if (pPolygon->touches(p1))
				cout << "接触" << endl;
			else if (pPolygon->overlaps(p1))
				cout << "部分重叠" << endl;
			else if (pPolygon->covers(p1))
				cout << "覆盖" << endl;
			else
				cout << *im << endl;
		}
	}
	system("pause");
    return 0;
}

输出结果如下：

其他几何对象之间的关系判断与此类似。

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